1. Field of the Invention
The present invention relates to a joint for connecting together reinforcing bars employed in concrete construction.
2. Description of the Related Art
A typical conventional joint of the type described above has, as shown in FIG. 9, a sleeve (a) with an oval cross section which serves as a joint main body and a wedge (b). To connect the reinforcing bars (c) and (d) together by using this joint, the respective end portions of the reinforcing bars are inserted into the joint in such a manner that they are respectively fitted into two curved portions of the joint, and the wedge (b) is press-fitted into wedge bores (e) which extend through the respective centers of two side walls of the sleeve (a) so that the end portions of the reinforcing bars (c) and (d) are pressed against the inner surfaces of the corresponding curved portions of the sleeve (a) and thereby rigidly secured between the wedge (b) and said surfaces, thus enabling the joint to resist any axial force applied to these reinforcing bars (c) and (d).
The above-described conventional joint for reinforcing bars employed in concrete construction suffers, however, from the following problems. Since each of the reinforcing bars (c) and (d) and the sleeve (a) are in contact with each other at only one point, the frictional resistance occurring between the reinforcing bars (c), (d) and the sleeve (a) which counteracts the force axially applied to the reinforcing bars (c) and (d) is relatively small, which means that it is undesirably easy for the reinforcing bars (c) and (d) to come out of the sleeve (a).
Although marketed reinforcing bars with a circular cross section are produced so that the outer diameters thereof are within tolerances regulated in accordance with J.I.S. (Japanese Industrial Standard), reinforcing bars which have annular or linear projections provided on the outer surfaces thereof are not subject to J.I.S. standards with respect to the outer diameters thereof, and they are standardized only in terms of the weight per unit length. For this reason, when such reinforcing bars are connected together by employing the conventional joint of the type described above, the clamping force of the joint differs in accordance with the outer diameters of the reinforcing bars employed, which means that it is impossible to effect an accurate and reliable connection.
In addition, the position of the projections provided on the above-described reinforcing bars relative to the inner surface of the sleeve differs in accordance with the circumferential orientation (i.e., orientation about the axis) of the reinforcing bars inserted into the sleeve, and this also inhibits the connection of reinforcing bars in a satisfactory condition.